1. Field of the Invention
This invention relates generally to the field of portable communication receivers, and in particular to portable communication receivers having selectively switched receiver battery saver functions.
2. Description of the Prior Art
In the current battery saver art, as it is practiced in paging receivers, all of the elements of the receiver portion of the paging receiver are switched ON and OFF simultaneously. This technique is shown in FIG. 1, which is an electrical block diagram of a typical prior art paging receiver. As shown in FIG. 1, the receiver portion of the paging receiver comprises a front end, or high conversion section 112 which includes a radio frequency (RF) amplifier 114, a first mixer 116, and a first oscillator 118. The supply of power to the front end 112 is controlled by a switched voltage regulator 120 which selectively supplies a regulated supply voltage from the battery to the front end 112 elements under control of a microcomputer decoder 122. The receiver portion of the paging receiver also comprises a back end, or low conversion section 124 which includes a second mixer 126, a second oscillator 128, an intermediate frequency (IF) amplifier 130, a demodulator 132, and an audio limiter 134. The supply of power to the second mixer 126, second oscillator 128, IF amplifier 130, demodulator 132, and audio limiter 134 is controlled by a switchable current source 136 which selectively supplies current to the back end 124 elements also under control of the microcomputer decoder 122. In the prior art paging receivers, both the front end 112 and back end 124 sections are simultaneously controlled by the microcomputer decoder 122 for the battery saving operation.
While the above technique has worked well in the past when the length of the ON period provided was considerably longer than the minimum turn-on time for each of the circuit elements in the receiver, the length of the receiver ON period in newer battery saving receivers are being of necessity shortened, due to a need to continue to reduce the average current drain of the receivers. The length of the receiver ON period for newer receiver designs are rapidly approaching the minimum turn-on times of many of the receiver functions, and in particular those of the oscillator circuits, voltage regulator circuits, and so on. There is a need to continue to provide even greater battery saving economy than currently available with the improvements obtained from ever shorter battery saver ON periods. Such continued battery savings improvements are not obtainable with the prior art techniques of switching power to the receiver portion of the paging receiver. An improved method for switching power to the receiver portion is required which will continue to enable reduction in the average current drain of paging receivers.